This invention relates generally to multiple glazed units and in particular to an improved spacer assembly for spacing apart the glass panes or glazing panels of such a unit.
As is well known in the art, in multiple glazed units, two or more glazing panels are secured in spaced apart parallel relationship to one another by peripheral edge spacers and adhered thereto by a suitable sealing composition applied between each panel and and the spacer. The spacer is often a hollow tubular spacer and it usually contains a desiccant to absorb moisture from the space between the glazing panels to thus avoid condensation problems. In the case of tubular spacers, the same are commonly roll-formed into the desired profile shape.
Many conventional spacer designs do not provide adequate space or room for the desiccant material. Hence, after a period of time, the moisture absorbing capability of the desiccant is exceeded and condensation begins to appear on the interior surfaces of the glazing panels.
Another problem common to conventional spacer designs is related to the fact that the inner wall of the spacer is readily visible and often presents a rather undesirable appearance in that it is not of the same colour as the frame surrounding the glazing unit. It is not practical to produce and market differently coloured spacer bars.
Another difficulty inherent in the pesent spacer arrangements is that they typically provide an easy path for the transmission of heat from one glazing panel to the other. As a result of this, under low temperature conditions, a frost line around the perimeter of the glazing unit is often present. Another problem is that a rigid spacer provides an excellent path for the transmission of sound from the outer panel to the inside panel. This poses a particular problem in high-noise areas such as airports. Other institutions such as hospitals also have a need for low sound transmission glazing units.
Another problem with conventional glazing units is related to the problem of deflection of the glazing panels under the influence of high winds, traffic noise, or internal pressure changes owing to expansion or contraction of the air mass contained within the glazing unit. This action imposes high stresses on the glazing panels and can break the seal between the spacer and the glazing units thus allowing moisture to enter and in extreme cases breakage of the glazing panel can occur.
Since the spacer must extend completely around the marginal portion of the glazing unit, special provisions must be made for the corners. In the most common constructions used to date, the spacer is miter-cut at the corner locations and spliced together by means of a special corner pieces. This creates a number of problems since the corner pieces and the required assembly procedure increases manufacturing costs substantially; moreover the spacer assembly is weaker at these corners and the corner piece assembly often affords a path for moisture to seep into the interior of the glazed unit from the outside.
Efforts have been made in the past to provide a spacer bar arrangement having right angle bends at the corners; however these designs do not appear to have found wide acceptance apparently because the bending process causes substantial distortion of the spacer tube profile and moreover, the strength at the bend is often significantly impaired.
In other instances it may be desirable to use muntin bars between the panes for decorative or reinforcement purposes. In the past it has been a problem to secure them securly to the spacers so there is no danger of them slipping out of position in response to vibration and the like.